On "Come Out, Come Out," the irresistible, horn-abetted highlight of I Was Totally Destroying It's second album, Horror Vacui, Rachel Hirsh returns to the plea "I want to be young" four times. "I want to be young/ to be a wreck and wrecked upon," she sings during the first iteration, the words of her wish falling squarely over a big, bouncing beat. Hirsh wants to make a mess of everything around her, to return to simplicity, to have a lot of fun.

The interesting irony, though, is that very little seems simple or elementary about Horror Vacui, a breakup album that thrives on the splitting-at-the-seams/ attached-in-the-mix chemistry of Hirsh and ex-boyfriend John Booker, who takes lead on about half of these songs and harmonies on the rest. Indeed, Horror Vacui pushes I Was Totally Destroying It beyond the bounds of a return to innocence and youth, into the territory of a mature band capable of crafting a great record. "Come Out, Come Out," after all, is a cry for rebellion that works because it's so tightly arranged and precisely executed. That is, it refines and cultivates a teenage urge. Compositionally smarter and structurally more diverse than you might've imagined, I Was Totally Destroying It bests their past on Horror Vacui by wrapping willful growth into irrepressible pop songs.

Across its debut LP and two EPs, I Was Totally Destroying It's calling card has been agile, aggressive power-pop buoyed by a sea of attitude. They again land about half a dozen such tunes: Opener "Beneath You All the Way" is Booker's racing, open-road anthem about trying to stick around for love, even when the odds (and the other party, it seems) shout otherwise. Its chewy bass and boisterous guitars frame the four excitable minutes as they charge beneath the harmonies like a cavalcade. On the shorter, hyperkinetic "A Reason To," Hirsh heads in the other direction, exclaiming "Either way, I'm going to find a reason to break." Booker's voice—ironically, passionately, perfectly—rises to meet hers in harmony.

But even within these radio-savvy molds, the songs twist adventurously. James Hepler creatively works dynamics into bombastic rock drumming, and Booker and Armstead's dual guitars snap between smart textural atmospheres and lean, slanted lines. Hirsh even phases her synthesizer into and out of time with the band at one point, making the moment when everything locks into place during the chorus that much more compelling. "Beneath" plummets from its straightforward clip after climbing a guitar riff with no end and peels away to nothing more than a single guitar and Hirsh's ethereal voice. "You can't drive me away," she sings, stealing Booker's words. They race back into it together, capitalizing on their own interpersonal drama.

Such structural intricacies extend beyond simply turning good pop songs into better pop songs, though: I Was Totally Destroying It has, at last, become best when writing outside of its familiar, frenetic trope, or at least when they're testing its limits. "Green Means Go," for instance, combines rock band basics and group chants in a way that suggests The Arcade Fire, while Booker sings as if he's on a see-saw, his brilliant leaps between notes bending the song into an oddball instrumental bridge that the band must shout its way out of. Several of Hirsh's lead turns, in particular, point to a broad sense of possibility—and the permanent anchor to hook—for the Chapel Hill quintet. The aforementioned "Come Out, Come Out" shakes itself free of the usual guitar focus, choosing instead to follow a rhythmic lead. And her fragile turn on "Cup of Tea," the quietest and most subtly crafted tune in the band's oeuvre, is gorgeous. Pensive and patient, she sounds like she'd wait all day for this whole thing to get better.

And that's my advice, too: It's long been easy to dismiss I Was Totally Destroying It as a chirpy pop band grafting local indie rock credibility onto songs that Get Up Kids, Saves the Day and, to a lesser extent, Paramore have already made famous. But Horror Vacui is better than that reductive gripe. It's a breathless album full of clashing spirits racing each other toward ever-expansive ideas. In the end, it's the sound of two people trying to forget each other separately while forging ahead together, their closest friends providing the score. It's a drama totally worth hearing.

I Was Totally Destroying It releases Horror Vacui with a show at Cat's Cradle Saturday, Oct. 10, with Lonnie Walker, Rat Jackson, Lake Inferior, Des Ark and magician Mike Casey. The $7-$10 show starts at 8:30 p.m.